The present invention relates to a percolator cup, particularly for espresso coffee machines.
In espresso coffee machines, the ground coffee is placed inside a filter cup housed removably inside a cup having at least one outlet conduit at the bottom, and connectable at the top, normally by means of a bayonet joint, to the outlet of a hot water supply device normally consisting of a boiler.
Correct performance of a machine of the aforementioned type depends on the grain size and the amount of ground coffee employed, and the extent to which it is compressed inside the filter cup. All of which factors combine to form, inside the filter cup, a wafer of such volume and consistency as to impede, when impregnated with hot water, outflow of the hot water through the outlet at the bottom, and generate inside the cup a pressure of normally about 10-12 atmospheres. It is known, in fact, that the quality of the espresso coffee produced depends on the temperature and pressure of the water or steam inside the percolator cup, and that no froth (which is the mark of a good espresso coffee) is formed below the above pressures.